Mini Split COP?

[Robaroni]

Originally Posted by jeff5may

Rob,

Pardon the tons of questions I'm about to ask, just trying to help.

How much, if any, of the heating solution are you planning on DIY?

How many BTU of heat will you need, especially at sub-zero ambient temperatures?

Is this thread about a small, supplemental heater, or the whole house?

Have you considered a water-to-water setup to heat your floor?

Do you have any kind of thermal store for your radiant floor?

Do you want to maximize energy savings, or just meet your (10% or less) demand on those extremely cold days?

Your answers to these questions will lead you in different directions. To provide heat to a 225 ft2 room at -20degF can be done with the right air-source minisplit at roughly 2/3 the electricity per BTU as an electric resistance heater. However, to maximize your energy savings year-round for the whole house, a completely different system would save you gobs more energy, yet may or may not cost a whole lot more. Better off is a matter of opinion.

Jeff,
The questions are fine, I'm looking for advice.
First, I built the house around 20 years ago. Oil heat, radiant tubes in the floors (6 x 200 ft. loops and a loop for the new room that isn't in the system yet). 100k boiler at 110 to 120F into the radiant.
I have a nice Tulikivi soap stone fireplace/bake oven that can carry the house in the winter if I need it too.

I originally thought about using the mini split for just the new room which adds about 225sq./ft. to make the house about 1800 sq./ft. but now I'm thinking I may try to go further. I thought about a deep well heat pump system that would cost me about 15k before rebates (2 to 3 ton) but I don't like the idea of running on electric either. First, I won't know till the spring how much I'm getting out of my added intertie/off grid this summer (added 4.2Kw to already 6.4Kw intertie). Right now (summer time) I'm making about 1 MWH, give or take, after my usage.
So ideally I guess I'll have to go with oil partially this winter to see what the figures show. Also, hopefully, I'll get a windmill or two up this summer and maybe a micro-hydro into the stream.
The house is well insulated and tight and the sun room I added a few years ago, helps when the sun comes out, even in the winter as it's on the south side of the house.
Rob
.

[Robaroni]

Originally Posted by Xringer

I just looked at the underground weather data for Meredith, NY and does get a lot colder up in the hills around there!
Around here, the coldest temps are very early in the AM..
But when the sun comes out, it's back up into the teens and twenties.
One of the advantages of living near the sea, I guess.

Even with your excessive cold stretches, if your average cold season temp is in the teens,
you still might find a good mini-split useful.. Ours does the job 99.4% of the time.
So, maybe up in those hills, it might be useful 80% of the time.?.
They work pretty well above 5F.. The new models do better..
http://i46.photobucket.com/albums/f1...CL/heatcap.jpg

Yes, I haven't counted it out just yet. One of things I like is that I can 'test the water' so to speak and see how it does, then make a decision when I've made some calculations.

I have a pretty good weather station here as I monitor the wind data in my front field, yes, just before dawn is usually the coldest.

Rob

[jeff5may]

If ultimate low temperature performance is what you're after, using an air-source mini-split, two lines come to mind:
1. Fujitsu Halcyon
2. Mitsubishi Hyper Heat

Of the two, the Mitsubishi boasts better heating numbers at low temps, favoring capacity over COP. It claims full rated capacity down to 5 degF and 70-75% of rated capacity at -13 degF. Can you say "hyperspeed compressor engage"?

For a boiler "replacement" unit, the Mitsu Ecodan system has been in widespread use in the UK for years, and has been well documented to meet demand down to -20.

[Mikesolar]

i need to find the test paper that I read but it says that the Mitsi numbers are not as good as they claim and are roughly on par with the Fujitsu and Panasanyo will be coming out with something much better shortly so there may be some competition. That said, it seems the holy grail would be to have one of these inverter units doing floor heat but we don't have the market yet to get the good stuff over from Europe. Damn scorched air.....ruined everything...LOL.

[Robaroni]

Originally Posted by Mikesolar

i need to find the test paper that I read but it says that the Mitsi numbers are not as good as they claim and are roughly on par with the Fujitsu and Panasanyo will be coming out with something much better shortly so there may be some competition. That said, it seems the holy grail would be to have one of these inverter units doing floor heat but we don't have the market yet to get the good stuff over from Europe. Damn scorched air.....ruined everything...LOL.

I've been running a 'cold' boiler into radiant floors for 20 years. I like radiant heat..... most of the time. The problem is when the sun drops below the horizon the temp drops very rapidly too. The system can't keep up with it so a spit mini might be just the thing to compensate for that. I like the idea of these things running without doing deep holes but I wonder what their numbers would be with them?

As far as radiant heat - no noise, maximize space, house runs cooler but feels warmer, no radiators ....
As far these commercials showing babies on a warm floor, if your floor is that warm you're melting candles!
Rob

[MN Renovator]

Originally Posted by Mikesolar

i need to find the test paper that I read but it says that the Mitsi numbers are not as good as they claim and are roughly on par with the Fujitsu and Panasanyo will be coming out with something much better shortly so there may be some competition. That said, it seems the holy grail would be to have one of these inverter units doing floor heat but we don't have the market yet to get the good stuff over from Europe. Damn scorched air.....ruined everything...LOL.

Panasonic has a few new arrivals recently in the AHRI directory and it looks to be giving Fujitsu a run for its money. I've personally been dismissing the Mitsubishi units because their efficiency ratings are not improving in line with the competition and since electricity and natural gas are split pretty heavily in MN with electricity being more expensive to heat with below freezing and with most of the overnight heating needs in Minnesota commonly being at or below 20f for 2 months of the year it puts plenty of pressure on high heating efficiency. The reality is that I'm using it more as a hedge against rising natural gas prices in the future while mostly being for their super efficiency cooling. The availability of excess electricity from my future array may be used for heat if we run into struggles with net metering to where it makes more sense to use it than sell it. *crossing fingers*

I'm personally looking at a 1 ton for cooling and the 13500 BTUhr at 17f of the Panasonic unit is actually enough to heat my house at 17f although the temperature might sag a bit when the unit defrosts. If I were to close the door and only heat my bedroom with it and let the rest of the house get cold it would likely cost very little to run in total heating cost in comparison to straight natural gas. 1 ton cooling will cover a 10 degree drop versus the outside temperature with no glass shading, so an 88 degree design day would have the house at 78 degrees which I can live with for the efficiency that these units provide and I'd likely give them a good head start cooling down to 68 degrees to get them ahead of the game and burn off humidity and then the mid/high 70's won't feel too bad. Worst case, I still have the oversized 8.5SEER 22,000 BTU beast to fill in the gaps in case the mini-split falls too far behind but I have a feeling I'd only be motivated to kick it on for 2 hours or so when we hit temperatures in the 90's while having others at the house and I'd still make sure the mini-split was taking the brunt of the load. Adding shading to the glass will likely make a 1 ton perfectly capable of covering the entire load as 10,000 BTUhr would cover more than 30 degrees difference of heat transfer through insulation and infiltration. Right now it seems that about 30% of my cooling is due to solar heating through the glass so I really need to cut that back.

.75 ton units
---
Panasonic CU-XE9PKUA
Cooling 8700BTUhr 16.1 EER, 28.5 SEER

Heating 12.5HSPF
12,000BTUhr at 47f and 10,600BTUhr at 17f
---
Fujitsu AOU9RLS2/ASU9RLS2
Cooling 9000BTUhr 16.1 EER, 27.2 SEER

Heating 12.5HSPF
12000BTUhr at 47f and 7300BTUhr at 17f
---

1 ton units
---
Panasonic CU-XE12PKUA
Cooling 11,500 14.35 EER, 25.5 SEER
Heating 12HSPF, 13,800 at 47f, 13,500 at 17f

Fujitsu AOU12RLS2/ASU12RLS2
Cooling 12,000 13.8 EER 25 SEER
Heating 12HSPF 16,000 at 47f and 9700 at 17f

[MN Renovator]

Originally Posted by Robaroni

..I like the idea of these things running without doing deep holes but I wonder what their numbers would be with them?

Inverter driven geothermal? According to the HVAC-Talk rumors coming from WaterFurnace demonstrations and trade conferences from a long time ago they are expecting nearly 6 COP with inverter driven geothermal with a properly sized loop field and non-full loads.

Apparently those are in service now though, they have 12 stages of capacity(20-130% nominal). Water flow is variable speed too. "Up to a 5.3 COP and 41 EER rated at 50% of capacity, even at stage 10 of 12(roughly 80% of capacity) the unit takes 2200 watts to operate the flow center, blower and compressor to heat the 3000 sq foot home this was installed in" http://hvac-talk.com/vbb/showthread....rnace-7-Series

[jeff5may]

MN,

I see your point about COP at sub-zero temps. With air-source units, there's no escaping the cliff at or around 20 degF. Either the unit loses heating capacity at slowly declining power draw or you increase power draw to maintain capacity. No two ways about it.

It looks to me like Mitsu fielded too many complaints from customers about their units not producing "hot" air in frigid outdoor conditions. With the hyper heat models, they went the way Hallowell did, increasing mass flow at the expense of COP. When outdoor temps take a dive, they "over-rev" the compressor to keep up first, then do something proprietary and secret with the multi-split units("hyper-rev" compressor? Flooded evap? Suction line hx? AUX heat? Anyone...anyone??) when it gets really cold. So now Joe Dirt or Joe Six-pack can't complain about Mr. Slim not keeping their trailers warm during the winter. They might pay 200 dollars a month more for that heat, but guess what? The dag nabbin thing does what it should when it's freezin outside.

Fuju and Panyo have chosen to try to maximize COP at the expense of sub-zero capacity. With larger outdoor coils and inverter compressors, they may over-rev a little, but not enough to injure efficiency. At Rob's -20 temps, they may only put out 1/3 of rated capacity, albeit at decent COP. To meet this condition, expect to spend double on an oversized unit that would then run at reduced capacity in milder weather at near water-source efficiency.

Either way, which unit to go with depends on the end goal. For a 225 sqft room, a 12k hyperheat or 15k rls2 would meet the need at -20f. For around 2000 dollars max.

[Robaroni]

Jeff,
Thanks,
I have one option I didn't mention. When it's 0F and below out I can close that room off. I won't get to play with my 'toys' in it but eventually it will warm up outside!
Rob

[Mikesolar]

Originally Posted by MN Renovator

Inverter driven geothermal? According to the HVAC-Talk rumors coming from WaterFurnace demonstrations and trade conferences from a long time ago they are expecting nearly 6 COP with inverter driven geothermal with a properly sized loop field and non-full loads.

Apparently those are in service now though, they have 12 stages of capacity(20-130% nominal). Water flow is variable speed too. "Up to a 5.3 COP and 41 EER rated at 50% of capacity, even at stage 10 of 12(roughly 80% of capacity) the unit takes 2200 watts to operate the flow center, blower and compressor to heat the 3000 sq foot home this was installed in" Inverter Geothermal Waterfurnace 7 Series

MN,
I'd be careful with the numbers supplied by ARI as it seems they don't take into account all the ancillary loads such as floor heat pumps or Desuperheat pump (sometimes). It has always been that way, IIRC.